Library of type and unit definitions

Package Contents


User's Guide of Units Library


Library of SI unit definitions


Type definitions of non SI and other units


Conversion functions to/from non SI units and type definitions of non SI units


Icons for Units


This information is part of the Modelica Standard Library maintained by the Modelica Association.

This package provides predefined types, such as Mass, Angle, Time, based on the international standard on units, e.g.,

type Angle = Real(final quantity = "Angle",
                  final unit     = "rad",
                  displayUnit   = "deg");

Some of the types are derived SI units that are utilized in package Modelica (such as ComplexCurrent, which is a complex number where both the real and imaginary part have the SI unit Ampere).

Furthermore, conversion functions from non SI-units to SI-units and vice versa are provided in subpackage Conversions.

For an introduction how units are used in the Modelica Standard Library with package Units, have a look at: How to use Units.

Copyright © 1998-2020, Modelica Association and contributors

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  • May 25, 2011 by Stefan Wischhusen:
    Added molar units for energy and enthalpy.
  • Jan. 27, 2010 by Christian Kral:
    Added complex units.
  • Dec. 14, 2005 by Martin Otter:
    Add User's Guide and removed "min" values for Resistance and Conductance.
  • October 21, 2002 by Martin Otter and Christian Schweiger:
    Added new package Conversions. Corrected typo Wavelenght.
  • June 6, 2000 by Martin Otter:
    Introduced the following new types
    type Temperature = ThermodynamicTemperature;
    types DerDensityByEnthalpy, DerDensityByPressure, DerDensityByTemperature, DerEnthalpyByPressure, DerEnergyByDensity, DerEnergyByPressure
    Attribute "final" removed from min and max values in order that these values can still be changed to narrow the allowed range of values.
    Quantity="Stress" removed from type "Stress", in order that a type "Stress" can be connected to a type "Pressure".
  • Oct. 27, 1999 by Martin Otter:
    New types due to electrical library: Transconductance, InversePotential, Damping.
  • Sept. 18, 1999 by Martin Otter:
    Renamed from SIunit to SIunits. Subpackages expanded, i.e., the SIunits package, does no longer contain subpackages.
  • Aug 12, 1999 by Martin Otter:
    Type "Pressure" renamed to "AbsolutePressure" and introduced a new type "Pressure" which does not contain a minimum of zero in order to allow convenient handling of relative pressure. Redefined BulkModulus as an alias to AbsolutePressure instead of Stress, since needed in hydraulics.
  • June 29, 1999 by Martin Otter:
    Bug-fix: Double definition of "Compressibility" removed and appropriate "extends Heat" clause introduced in package SolidStatePhysics to incorporate ThermodynamicTemperature.
  • April 8, 1998 by Martin Otter and Astrid Jaschinski:
    Complete ISO 31 chapters realized.
  • Nov. 15, 1997 by Martin Otter and Hubertus Tummescheit:
    Some chapters realized.